In front of the radiator.
The horn for the Mazda 3 is located below the drivers side headlight. The easiest way to reach it is by taking off the plastic piece on the bottomside of the vehicle. The horn will be mounted on a bracket. The single wire connected to the horn is power, the bracket is ground.
horn circuit mazda bt 50
Need to know how to fix the horn on a 1997 mazda millenia that doesn't work?
Replace it.
The horns themselves are hidden behind the front bumper.
Below are attached links discussing the horn on your truck.
Then you have a short in the wiring, the horn button is defective, or the horn itself is defective.
If it is anything like my 1994 MX-3, it is located under the bumper/side fender on the driver's side.
on our 99, i have to remove the headlite assembly to get to the horn. there is one on each side
The horn fuse is the same as the stop lamp fuse
in the stearing wheel